Really stuck and no idea what I am doing wrong! So I have the data that I need in tabular format.

The data is a summary of YTD savings by month/year and performs a lookup to determine how much is carried forward from the previous year.

LOOKUP(sum([Next_Yr_Savings]),-1)

I then want to plot this in a line chart and when I try I get a message saying "the table calculation requires a field that is missing, please add to the view". I have been messing about with this for a day and when I do manage to get a line chart it then has the balance carried forward from the previous year missing - in other words, the lookup calculation no longer works.